Novel Terpenoids with Potential Anti-Alzheimer Activity from Nepeta obtusicrena
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Dichloromethane extract of Nepeta obtusicrena Boiss. Et Kotschy Ex Hedge afforded two novel terpenoids, a diterpenoid and a triterpenoid in addition to two known triterpenoids, oleanolic acid and ursolic acid. Purification of the diterpenoid was carried out by HPLC, and its structure was elucidated as 14a-acetoxy-6-oxo-abieta-7-ene, and structure of the triterpenoid was elucidated as 2 alpha, 3 beta, 19 alpha, 24-tetrahydroxy-11-oxo-olean-12-ene. Both of the novel terpenes were obtained from nature for the first time and named as obtusicrenone and nemrutolone, respectively. Anticholinesterase (anti-Alzheimer) and antioxidant activities [DPPH free radical scavenging activity, ABTS cation radical scavenging activity, lipid peroxidation inhibitory activity, CUPRAC (Cupric Reducing Antioxidant Capacity)] of the dichloromethane and methanol extracts and the isolated four terpenoids were investigated. Both of the extracts and the isolated four terpenoids exhibited high anticholinesterase activity, particularly against acetylcholinesterase (AChE) enzyme. None of the samples tested showed high antioxidant activity.